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silica composite fibers prepared via dry-jet wet spinning process
Materials Letters 64 (2010) 1875–1878
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Characterization and mechanical properties of polyacrylonitrile/silica composite fibers prepared via dry-jet wet spinning process A. Mataram a,b, A.F. Ismail a,⁎, D.S.A. Mahmod a, T. Matsuura c a b c
Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 UTM, Skudai, Johor, Malaysia Department of Mechanical Engineering, Sriwijaya University, Sumatera Selatan, Indonesia Department of Chemical Engineering, Industrial Membrane Research Institute, University of Ottawa, Ont., Canada KIN 6N5
a r t i c l e
i n f o
Article history: Received 9 April 2010 Accepted 18 May 2010 Available online 2 June 2010 Keywords: Composite material Spinning process Fiber technology Mechanical properties
a b s t r a c t Polyacrylonitrile (PAN)/silica composite fibers were fabricated by dry-jet wet spinning process. PAN/silica composite fibers were characterized with SEM and FTIR. The former revealed that beads were formed and aggregated when silica content was more than 1 wt.%, while the latter confirmed the presence and increment of silica content. The tensile test was performed to obtain the mechanical properties of PAN/silica composite fibers, which showed an optimum Young's modulus at 5.94 GPa and tensile strength at 1.07 MPa at 1 wt.% silica. Therefore, the addition of silica particle at 1 wt.% has enhanced the mechanical properties of PAN/silica composite fibers. © 2010 Elsevier B.V. All rights reserved.
1. Introduction High strength and modulus of carbon fibers make them useful for the reinforcement of polymers, metals, carbons, and ceramics, despite their brittle nature. In the market, carbon fibers are dominated by fibers made from polyacrylonitrile (PAN) due to their combination of good mechanical properties (high strength, low-density composite materials and high break strength) particularly tensile strength, and reasonable cost [1]. In addition, numerous studies have shown that the PAN fibers possess the following characteristics; small diameter, maximum crystallinity, low comonomer contents and high modulus for the preparation of good quality carbon fibers [2–4]. Young's modulus of PAN precursor fibers seems the best parameters to represent the performance of carbon fibers since there is direct correlation between the Young's modulus of primary precursor and that of the resulting carbon fibers [5]. Therefore, the conditions of PAN fiber fabrication process play an important role in the production of high performance carbon fibers since the properties of PAN precursor fibers depend much on it [6]. Many research groups have been working on fabricating PAN based composite nanofibers, such as PAN/TiO2 [7], PAN/carbon nanotube [8] and PAN/Fe3O4 [9]. However, there are still few reports about the preparation and characterization of PAN/silica composite nanofibers, which may combine both the advantages of PAN such as light weight, flexibility, and good moldability, and of silica nanopar-
⁎ Corresponding author. Tel.: + 60 7 5535592; fax: + 60 7 5581463. E-mail address: [email protected] (A.F. Ismail). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.05.031
ticles such as high strength, excellent heat-stability, and good chemical resistance [2]. In the present work, PAN fibers were prepared by the dry-jet wet spinning method via PAN solution in N,Ndimethylformamide (DMF) and acrylamide (AM) containing silica nanoparticles. Structures of fibers were characterized by FTIR and SEM, while tensile test of PAN fibers were performed to evaluate their potential to be used as a precursor for carbon fibers. 2. Experimental PAN, DMF, AM and fumed silica nanoparticles were obtained from Aldrich Chemical and were used without further purification. Fumed silica nanoparticles have an average primary particle size of 14 nm. Dope solutions were prepared by dispersing predetermined amount of silica nanoparticles (0, 0.5, 1 and 2 wt.% to PAN) into wt.% PAN solution in DMF. The dope was mechanically stirred for at least 24 h at 60 °C in order to obtain homogeneous silica-dispersed PAN solutions [10]. The dry-jet wet spinning method was used to fabricate PAN fibers. The coagulation bath temperature was set at 17 °C. The fibers were collected onto a wind-up drum which was 17 cm in diameter. Next, the fibers were stretched and tied onto the metal net and underwent a drying process at room temperature for 24 h. 3. Characterization methods Scanning Electron Microscopy (SEM) was used to observe the morphology of PAN fiber cross-sectional structure. The FTIR Nicolet Magna-IR560, potassium bromide (KBr) type, was used to identify and classify the functional groups of PAN/silica fibers with various silica contents. Tensile test of PAN fibers was performed using tensile
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A. Mataram et al. / Materials Letters 64 (2010) 1875–1878
Fig. 1. SEM comparison of dry-jet wet spun PAN/silica composite fiber with different silica contents. (A) 0.5 wt.%, (B) 1 wt.% and (C) 2 wt.%.
tester machine (LRx2.5 KN LLYOD Instrument with a load cell of 1 N, accordance with ASTM D 3379 (25 mm gauge length are used for each PAN fibers) [11]. The tensile specimen was prepared by fixing the filament on a paper holder with an instant cyanoacrylate adhesive [12], while its gauge length, L was 25 mm and crosshead speed was 5 mm/min [13]. The tensile test, σ, gives a load, P as a function of extension, df is the function of diameter of fiber. Tensile stress was calculated as follows: σ = P / (πd2f / 4). 4. Results and discussion SEM micrographs of PAN/silica fiber surfaces with various silica contents are shown in Fig. 1. As can be seen, when the silica content was at 0.5 and 1 wt.%, the dispersion of silica nanoparticles was
relatively homogeneous in the PAN matrix. With the increase of silica content, the fiber shows greater aggregation or agglomeration of silica nanoparticles. At high silica content (2 wt.%), the dispersibility of silica in PAN fiber seems to be more difficult, which may contribute to the final irregular surface morphology of fiber. The cross-sectional structures of pure PAN and PAN/silica fibers with various silica contents are shown in Fig. 2. When the fiber is without silica (Fig. 2(A)) finger-like pores are observed, extending from the circumference to the center of the fiber. These finger-like pores were formed during the solvent or nonsolvent exchange that occurred in the coagulation bath. When the fibers contain silica particles (Fig. 2(B) and (C)), several spherical particles are observed. However, judging from the size of the silica nanoparticles (14 nm) these are the aggregates of individual nanoparticles. When silica
Fig. 2. The cross-sectional structures PAN/silica composite fiber with different silica contents. (A) 0 wt.% (pure PAN), (B) 0.5 wt.%, (C) 1 wt.% and (D) 2 wt.%.
A. Mataram et al. / Materials Letters 64 (2010) 1875–1878
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Fig. 3. FTIR spectra of PAN/silica composite fibers with different silica contents. (A) 0 wt.% (pure PAN), (B) 0.5 wt.%, (C) 1 wt.% and (D) 2 wt.%.
content is increased to 2 wt.% (Fig. 2(D)), further particle aggregation proceeds, resulting in larger aggregate sizes and is a result of pull out at failure [13]. Fig. 3 represents the FTIR spectra of PAN/silica composite fibers with different silica contents. Typically, PAN spectrum shows the bands in the region of 2913, 2245, 1457 and 1372 cm− 1 indicating the characteristics of stretching vibrations of alkanes, stretching vibration of the nitrile group (C≡N) and bending vibrations of (–CH3) and (–CH2) groups, respectively. The peaks at bands of 2342 and 1632 cm− 1 displayed the characteristics of CO2 due to instrumental condition and C O groups indicating the presence of AM. Comparing with pure PAN and PAN/silica with various silica contents, the peaks of Si–O–Si stretching vibrations can obviously be seen in the regions of 1167, 1114 and 1066 cm− 1 in sample D due to the increment of silica content up to 2 wt.%. Therefore, FTIR spectrum confirms the presence of Si–O–Si group in Fig. 3 (Sample B, C and D) with the increase of silica contents from 0.5 to 2 wt.%. Fig. 4 shows that with the increase of silica composition, the Young's modulus of PAN/silica composite fibers have increased as well. This result was in agreement with the reported work by Ji et al. [10]. Young's modulus has increased from 2.82 GPa to 5.94 GPa when the composition of silica increased from 0 wt.% to 1 wt.%. The tensile strength of PAN/silica composite fibers also showed an increment from 286 kPa to 1.07 MPa as observed in Fig. 4(B). Furthermore, silica particle has also influenced the mechanical properties of fibers. Young's modulus and tensile strength values decreased to 3.14 GPa and 299 kPa respectively when silica composition was added up to 2 wt.%. Here, Young's modulus and tensile strength values have dramatically depleted when the silica content increased more than 1 wt.%. These results are at least consistent with the hypothesis that several mechanical properties of PAN/silica composite fibers will be limited by composition of silica on fibers [10]. Therefore, when these silica particles were increased to 2 wt.%, the fibers will be more brittle and fragile. This is caused by the silica aggregation [13].
enhancement of silica content at 1 wt.% however decreased when the silica content proceed to 2 wt.%. The addition of silica particles more than 1 wt.%. produced more brittle and fragile PAN/silica composite fibers.
5. Conclusion This study represents the PAN/silica composite fibers prepared by dry-jet wet spinning process with different levels of silica contents. SEM micrographs reveal that beads were formed and aggregated when the silica contents were higher than 1 wt.%. The presence of silica contents was confirmed by FTIR. This study elucidate that Young's modulus and tensile strength increased according to the
Fig. 4. The tensile strength (A) and Young's modulus (B) of PAN/silica composite fibers with the change of silica composition (wt.%) respectively.
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A. Mataram et al. / Materials Letters 64 (2010) 1875–1878
Acknowledgement The authors would like to acknowledge the Ministry of Science, Technology and Innovation of Malaysia (MOSTI) for funding this research under project no. 03-01-06-SF0258 79136 Science Fund and 03-02-06-0060-PR0072/08-03-74539 Priorities Research. References [1] Rahaman MSA, Ismail AF, Mustafa A. Polym Degrad and Stab 2007;92:1421–32. [2] Donnet JB, Bansal R. Carbon Fibres. NewYork: Marcel Dekker; 1990.
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Mittal J, Mathur RB, Bahl OP. Carbon 1997;35:1713–22. Bahl OP, Mathur OB, Kundra KD. Fibre Sci Technol 1981;15:155–62. Chari SS, Bahl OP, Mathur RB. Fibre Sci Technol 1981;15:153–5. Ismail AF, Rahman MA, Mustafa A, Matsura T. Mater Sci Eng A 2008;485:251–7. Gurunathan K, Amalnerkar DP, Trivedi DC. Mater lett 2003;57:1642–8. Han GC, Sreekumar TV, Uchida T, Kumar S. Polymer 2005;46:10925–35. Zhang D, Karki AB, Rutman D, Young DP, Wang A, Cocke D, et al. Polymer 2009;50: 4189–98. Ji L, Zhang X. Mater Lett 2008;62:2161–4. Chen JC, Harrison IR. Carbon 2002;40:25–45. Sung MG, Sassa K, Tagawa T, Miyata T, Ogawa H, Doyama M. Carbon 2002;40:2013–20. Naito K, Tanaka Y, Yang JM, Kagawa Y. Carbon 2008;46:189–95.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Characterization and mechanical properties of polyacrylonitrile/silica composite fibers prepared via dry-jet wet spinning process A. Mataram a,b, A.F. Ismail a,⁎, D.S.A. Mahmod a, T. Matsuura c a b c
Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 UTM, Skudai, Johor, Malaysia Department of Mechanical Engineering, Sriwijaya University, Sumatera Selatan, Indonesia Department of Chemical Engineering, Industrial Membrane Research Institute, University of Ottawa, Ont., Canada KIN 6N5
a r t i c l e
i n f o
Article history: Received 9 April 2010 Accepted 18 May 2010 Available online 2 June 2010 Keywords: Composite material Spinning process Fiber technology Mechanical properties
a b s t r a c t Polyacrylonitrile (PAN)/silica composite fibers were fabricated by dry-jet wet spinning process. PAN/silica composite fibers were characterized with SEM and FTIR. The former revealed that beads were formed and aggregated when silica content was more than 1 wt.%, while the latter confirmed the presence and increment of silica content. The tensile test was performed to obtain the mechanical properties of PAN/silica composite fibers, which showed an optimum Young's modulus at 5.94 GPa and tensile strength at 1.07 MPa at 1 wt.% silica. Therefore, the addition of silica particle at 1 wt.% has enhanced the mechanical properties of PAN/silica composite fibers. © 2010 Elsevier B.V. All rights reserved.
1. Introduction High strength and modulus of carbon fibers make them useful for the reinforcement of polymers, metals, carbons, and ceramics, despite their brittle nature. In the market, carbon fibers are dominated by fibers made from polyacrylonitrile (PAN) due to their combination of good mechanical properties (high strength, low-density composite materials and high break strength) particularly tensile strength, and reasonable cost [1]. In addition, numerous studies have shown that the PAN fibers possess the following characteristics; small diameter, maximum crystallinity, low comonomer contents and high modulus for the preparation of good quality carbon fibers [2–4]. Young's modulus of PAN precursor fibers seems the best parameters to represent the performance of carbon fibers since there is direct correlation between the Young's modulus of primary precursor and that of the resulting carbon fibers [5]. Therefore, the conditions of PAN fiber fabrication process play an important role in the production of high performance carbon fibers since the properties of PAN precursor fibers depend much on it [6]. Many research groups have been working on fabricating PAN based composite nanofibers, such as PAN/TiO2 [7], PAN/carbon nanotube [8] and PAN/Fe3O4 [9]. However, there are still few reports about the preparation and characterization of PAN/silica composite nanofibers, which may combine both the advantages of PAN such as light weight, flexibility, and good moldability, and of silica nanopar-
⁎ Corresponding author. Tel.: + 60 7 5535592; fax: + 60 7 5581463. E-mail address: [email protected] (A.F. Ismail). 0167-577X/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2010.05.031
ticles such as high strength, excellent heat-stability, and good chemical resistance [2]. In the present work, PAN fibers were prepared by the dry-jet wet spinning method via PAN solution in N,Ndimethylformamide (DMF) and acrylamide (AM) containing silica nanoparticles. Structures of fibers were characterized by FTIR and SEM, while tensile test of PAN fibers were performed to evaluate their potential to be used as a precursor for carbon fibers. 2. Experimental PAN, DMF, AM and fumed silica nanoparticles were obtained from Aldrich Chemical and were used without further purification. Fumed silica nanoparticles have an average primary particle size of 14 nm. Dope solutions were prepared by dispersing predetermined amount of silica nanoparticles (0, 0.5, 1 and 2 wt.% to PAN) into wt.% PAN solution in DMF. The dope was mechanically stirred for at least 24 h at 60 °C in order to obtain homogeneous silica-dispersed PAN solutions [10]. The dry-jet wet spinning method was used to fabricate PAN fibers. The coagulation bath temperature was set at 17 °C. The fibers were collected onto a wind-up drum which was 17 cm in diameter. Next, the fibers were stretched and tied onto the metal net and underwent a drying process at room temperature for 24 h. 3. Characterization methods Scanning Electron Microscopy (SEM) was used to observe the morphology of PAN fiber cross-sectional structure. The FTIR Nicolet Magna-IR560, potassium bromide (KBr) type, was used to identify and classify the functional groups of PAN/silica fibers with various silica contents. Tensile test of PAN fibers was performed using tensile
1876
A. Mataram et al. / Materials Letters 64 (2010) 1875–1878
Fig. 1. SEM comparison of dry-jet wet spun PAN/silica composite fiber with different silica contents. (A) 0.5 wt.%, (B) 1 wt.% and (C) 2 wt.%.
tester machine (LRx2.5 KN LLYOD Instrument with a load cell of 1 N, accordance with ASTM D 3379 (25 mm gauge length are used for each PAN fibers) [11]. The tensile specimen was prepared by fixing the filament on a paper holder with an instant cyanoacrylate adhesive [12], while its gauge length, L was 25 mm and crosshead speed was 5 mm/min [13]. The tensile test, σ, gives a load, P as a function of extension, df is the function of diameter of fiber. Tensile stress was calculated as follows: σ = P / (πd2f / 4). 4. Results and discussion SEM micrographs of PAN/silica fiber surfaces with various silica contents are shown in Fig. 1. As can be seen, when the silica content was at 0.5 and 1 wt.%, the dispersion of silica nanoparticles was
relatively homogeneous in the PAN matrix. With the increase of silica content, the fiber shows greater aggregation or agglomeration of silica nanoparticles. At high silica content (2 wt.%), the dispersibility of silica in PAN fiber seems to be more difficult, which may contribute to the final irregular surface morphology of fiber. The cross-sectional structures of pure PAN and PAN/silica fibers with various silica contents are shown in Fig. 2. When the fiber is without silica (Fig. 2(A)) finger-like pores are observed, extending from the circumference to the center of the fiber. These finger-like pores were formed during the solvent or nonsolvent exchange that occurred in the coagulation bath. When the fibers contain silica particles (Fig. 2(B) and (C)), several spherical particles are observed. However, judging from the size of the silica nanoparticles (14 nm) these are the aggregates of individual nanoparticles. When silica
Fig. 2. The cross-sectional structures PAN/silica composite fiber with different silica contents. (A) 0 wt.% (pure PAN), (B) 0.5 wt.%, (C) 1 wt.% and (D) 2 wt.%.
A. Mataram et al. / Materials Letters 64 (2010) 1875–1878
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Fig. 3. FTIR spectra of PAN/silica composite fibers with different silica contents. (A) 0 wt.% (pure PAN), (B) 0.5 wt.%, (C) 1 wt.% and (D) 2 wt.%.
content is increased to 2 wt.% (Fig. 2(D)), further particle aggregation proceeds, resulting in larger aggregate sizes and is a result of pull out at failure [13]. Fig. 3 represents the FTIR spectra of PAN/silica composite fibers with different silica contents. Typically, PAN spectrum shows the bands in the region of 2913, 2245, 1457 and 1372 cm− 1 indicating the characteristics of stretching vibrations of alkanes, stretching vibration of the nitrile group (C≡N) and bending vibrations of (–CH3) and (–CH2) groups, respectively. The peaks at bands of 2342 and 1632 cm− 1 displayed the characteristics of CO2 due to instrumental condition and C O groups indicating the presence of AM. Comparing with pure PAN and PAN/silica with various silica contents, the peaks of Si–O–Si stretching vibrations can obviously be seen in the regions of 1167, 1114 and 1066 cm− 1 in sample D due to the increment of silica content up to 2 wt.%. Therefore, FTIR spectrum confirms the presence of Si–O–Si group in Fig. 3 (Sample B, C and D) with the increase of silica contents from 0.5 to 2 wt.%. Fig. 4 shows that with the increase of silica composition, the Young's modulus of PAN/silica composite fibers have increased as well. This result was in agreement with the reported work by Ji et al. [10]. Young's modulus has increased from 2.82 GPa to 5.94 GPa when the composition of silica increased from 0 wt.% to 1 wt.%. The tensile strength of PAN/silica composite fibers also showed an increment from 286 kPa to 1.07 MPa as observed in Fig. 4(B). Furthermore, silica particle has also influenced the mechanical properties of fibers. Young's modulus and tensile strength values decreased to 3.14 GPa and 299 kPa respectively when silica composition was added up to 2 wt.%. Here, Young's modulus and tensile strength values have dramatically depleted when the silica content increased more than 1 wt.%. These results are at least consistent with the hypothesis that several mechanical properties of PAN/silica composite fibers will be limited by composition of silica on fibers [10]. Therefore, when these silica particles were increased to 2 wt.%, the fibers will be more brittle and fragile. This is caused by the silica aggregation [13].
enhancement of silica content at 1 wt.% however decreased when the silica content proceed to 2 wt.%. The addition of silica particles more than 1 wt.%. produced more brittle and fragile PAN/silica composite fibers.
5. Conclusion This study represents the PAN/silica composite fibers prepared by dry-jet wet spinning process with different levels of silica contents. SEM micrographs reveal that beads were formed and aggregated when the silica contents were higher than 1 wt.%. The presence of silica contents was confirmed by FTIR. This study elucidate that Young's modulus and tensile strength increased according to the
Fig. 4. The tensile strength (A) and Young's modulus (B) of PAN/silica composite fibers with the change of silica composition (wt.%) respectively.
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A. Mataram et al. / Materials Letters 64 (2010) 1875–1878
Acknowledgement The authors would like to acknowledge the Ministry of Science, Technology and Innovation of Malaysia (MOSTI) for funding this research under project no. 03-01-06-SF0258 79136 Science Fund and 03-02-06-0060-PR0072/08-03-74539 Priorities Research. References [1] Rahaman MSA, Ismail AF, Mustafa A. Polym Degrad and Stab 2007;92:1421–32. [2] Donnet JB, Bansal R. Carbon Fibres. NewYork: Marcel Dekker; 1990.
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]
Mittal J, Mathur RB, Bahl OP. Carbon 1997;35:1713–22. Bahl OP, Mathur OB, Kundra KD. Fibre Sci Technol 1981;15:155–62. Chari SS, Bahl OP, Mathur RB. Fibre Sci Technol 1981;15:153–5. Ismail AF, Rahman MA, Mustafa A, Matsura T. Mater Sci Eng A 2008;485:251–7. Gurunathan K, Amalnerkar DP, Trivedi DC. Mater lett 2003;57:1642–8. Han GC, Sreekumar TV, Uchida T, Kumar S. Polymer 2005;46:10925–35. Zhang D, Karki AB, Rutman D, Young DP, Wang A, Cocke D, et al. Polymer 2009;50: 4189–98. Ji L, Zhang X. Mater Lett 2008;62:2161–4. Chen JC, Harrison IR. Carbon 2002;40:25–45. Sung MG, Sassa K, Tagawa T, Miyata T, Ogawa H, Doyama M. Carbon 2002;40:2013–20. Naito K, Tanaka Y, Yang JM, Kagawa Y. Carbon 2008;46:189–95.